1. Field of the Invention
The present invention relates generally to multimodal auditory prostheses and, more particularly, to wireless communication in a multimodal auditory prosthesis.
2. Related Art
Hearing loss is generally of two types, namely conductive and sensorineural. Conductive hearing loss occurs when the normal mechanical pathways that provide sound to hair cells in the cochlea are impeded, for example, by damage to the ossicular chain or to the ear canal. Individuals suffering from conductive hearing loss typically have some form of residual hearing because the hair cells in the cochlea are undamaged. As a result, such individuals typically receive an auditory prosthesis that delivers acoustic or mechanical energy to the ear. For example, acoustic energy may be delivered through a column of air to the tympanic membrane (eardrum) via a hearing aid residing in the ear canal. Mechanical energy may be delivered via the physical coupling of a mechanical transducer (i.e. a transducer that converts electrical signals to mechanical motion) to the tympanic membrane, the skull, the ossicular chain, the round or oval window of the cochlea or other structure that will result in the application of the imposed mechanical energy to the hydro-mechanical system of the cochlea.
Sensorineural hearing loss occurs when there is damage to the inner ear, or to the nerve pathways from the cochlea to the brain. As such, those suffering from sensorineural hearing loss are thus unable to derive suitable benefit from auditory prostheses that deliver acoustic or mechanical energy. As a result, auditory prostheses that electrical stimulation signals to nerve cells of the recipient's auditory system have been developed to provide such individuals with the ability to perceive sound.
For example, cochlear implants are generally recommended when the sensorineural hearing loss is due to the absence or destruction of the cochlea hair cells which transduce acoustic signals into nerve impulses. Cochlear implants electrically stimulate a recipient's cochlea by directly delivering direct electrical stimulation signals to the auditory nerve cells, thereby bypassing absent or defective hair cells that normally transduce acoustic vibrations into neural activity. Such devices generally use an electrode array implanted in the cochlea so that the electrodes may differentially activate auditory neurons that normally encode differential pitches of sound.
In circumstances in which the electrical impulses generated by the cochlea are not delivered to the brain due to disease, injury or absence of the spiral ganglion cells or auditory nerve, another type of electrically-stimulating hearing prosthesis referred to as an auditory brain implant (ABI) is generally recommended. ABIs provide electrical stimulation directly to the auditory cortex of the brain via an array of electrodes.
As noted, the treatment of both conductive and sensorineural hearing loss has been quite different, relying on two different principles to deliver sound signals to be perceived by the brain as sound. Furthermore, it is relatively common in hearing impaired individuals to experience severe sensorineural hearing loss for sounds in the high frequency range, and yet still be able to discern sounds in the middle to low frequency range. Traditionally, such recipients receive treatment to preserve and/or improve perception of the middle to low frequency sounds using, for example, an auditory prosthesis that delivers acoustic or mechanical stimulation, and little is done to restore the severe hearing loss of high frequency sounds.
More recently, there has been an increased interest in multimodal auditory prostheses that are capable of using multiple types of stimulation to stimulate a recipient's ear. Using multiple types of stimulation provides a recipient with the ability to perceive a wider range of frequencies regardless of the cause of hearing loss. One exemplary type of multimodal prosthesis utilizes electrical and acoustical stimulation, commonly referred to as an Electro-Acoustical Stimulation (EAS) device. In EAS devices, acoustic stimulation is used to amplify the low frequencies of the received sound while electrical stimulation is used to provide the recipient with the ability to perceive middle and high frequencies of the sound.